• Title/Summary/Keyword: Tetra mesh

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A study on the finite element modeling of femur based marching cube algorithm (Marching cube 알고리즘을 이용한 대퇴골의 유한요소 모델링에 관한 연구)

  • 곽명근;오택열;변창환;이은택;유용석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.1074-1077
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    • 2002
  • Biomechanical behavior of the human femur is very important in various clinical situations. In this study, the data of FE models based on DICOM file exported from Computed tomography(CT). We generated FE models(voxel model, tetra model) of human femur using CT slide image. We compared them with Yon Mises stress results derived from finite element analysis(FEA). Comparing the two models, we found a correlation of them. As a result, the tetra model based proposed marching cube algorithm is a valid and accurate method to predict parameters of the complex biomechanical behavior of human femur.

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Evaluation of Turbulent Models on the Swirling Flow of a Gun-Type Gas Burner According to the Mesh Size (격자크기에 따른 Gun식 가스버너의 스월유동에 대한 난류모델평가)

  • Kim, Jang-Kweon;Oh, Seok-Hyung
    • Journal of Power System Engineering
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    • v.18 no.3
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    • pp.59-65
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    • 2014
  • The computational fluid dynamics was carried out to evaluate turbulent models on the swirling flow of a gun-type gas burner(GTGB) according to the mesh size. The commercial SC/Tetra software was used for a steady-state, incompressible and three-dimensional numerical analysis. In consequence, the velocity magnitude from the exit of a GTGB and the flowrate predicted by the turbulent models of MP k-${\varepsilon}$, Realizable k-${\varepsilon}$ and RNG k-${\varepsilon}$ agree with the results measured by an experiment very well. Moreover, the turbulent kinetic energy predicted by the turbulent model of standard k-${\varepsilon}$ with mesh type C only agrees with the experimental result very well along the radial distance. On the other hand, the detailed prediction of the information of swirling flow field near the exit of a GTGB at least needs a CFD analysis using a fairly large-sized mesh such as a mesh type C.

Fabrication of Anti-Reflection Thin Film by Using Screen Printing Method (Screen Printing법을 이용한 반사방지막 제조)

  • Choi, Chang-Sik;Nam, Jeong-Sic;Lee, Ji-Sun;Jeon, Dae-Woo;Lee, Young-jin;Bae, Hyun;Kim, Jin-Ho
    • Korean Journal of Materials Research
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    • v.28 no.12
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    • pp.714-718
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    • 2018
  • Anti-reflection thin films are fabricated on glass substrates using the screen printing method. Tetra ethyl silicate(TEOS) and methyl tri methoxy silane(MTMS) are used as starting materials and buthyl carbitol acetate(BCA) and buthyl cellusolve(BC) are mixed to improve the viscosity of the solution. Anti-reflection thin films are fabricated according to the number of the screen mesh and the characteristics improve as the mesh size increases. The transmittance and reflectance of the coated thin film using 325 mesh are about 94 % and 0.43 % in the visible wavelength. The thickness and refractive index of the AR thin film are 107 nm and n = 1.26, respectively.

PULSATILE FLOW SIMULATION OF A NON-NEWTONIAN FLUID THROUGH A BIFURCATION TUBE USING THE CFD ANALYSIS (CFD를 이용한 분지관 비뉴턴 해석)

  • Hwang, D.;Yoo, S.S.;Park, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.177-180
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    • 2008
  • The objective of this study is to get simulation data about pulsatile flow of a non-Newtonian fluid through a bifurcated tube. All the process was based on CFD method, with a commercial FVM code, SC/Tetra ver. 6.0 for solving, and with CATIA R16 for generating geometries. To define a non-Newtonian fluid, the following viscous models are used; the Powell-Eyring model, the modified Powell-Eyring model, the Cross model, the modified Cross model, the Carreau model, the Carreau-Yasuda model and the modified Power Law model. The flow calculation data using each model were compared with the other data of a existing paper. Finally, the Carreau model was recognized to give the best result with the SC/Tetra code, and the succeeding simulations are made with the model. For the pulsating flow condition, the sine wave type velocity profile is given as the inlet boundary condition. To investigate the effect of geometries and mesh, the pre-test is carried out with various curvature conditions of the bifurcated corner, and then with various mesh conditions. The final process is to calculate flow variables such as the wall shear stress (WSS) and the wall shear stress gradient (WSSG). To validate all the result, the simulation is compared with the existing data of the other papers. Generally speaking, there is a noticeable difference in the maximum and minimum value of WSS. It is not sure that the values in each data are on the exactly same location. However, the overall trend is similar. The next study needs to investigate the same situation by experimental method. Furthermore, if the flow is simulated with more pulsatile conditions, more data of flow field through a bifurcated tube could be achieved.

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PULSATILE FLOW SIMULATION OF A NON-NEWTONIAN FLUID THROUGH A BIFURCATION TUBE USING THE CFD ANALYSIS (CFD를 이용한 분지관 비뉴턴 해석)

  • Hwang, D.;Yoo, S.S.;Park, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.177-180
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    • 2008
  • The objective of this study is to get simulation data about pulsatile flow of a non-Newtonian fluid through a bifurcated tube. All the process was based on CFD method, with a commercial FVM code, SC/Tetra ver. 6.0 for solving, and with CATIA R16 for generating geometries. To define a non-Newtonian fluid, the following viscous models are used; the Powell-Eyring model, the modified Powell-Eyring model, the Cross model, the modified Cross model, the Carreau model, the Carreau-Yasuda model and the modified Power Law model. The flow calculation data using each model were compared with the other data of a existing paper. Finally, the Carreau model was recognized to give the best result with the SC/Tetra code, and the succeeding simulations are made with the model. For the pulsating flow condition, the sine wave type velocity profile is given as the inlet boundary condition. To investigate the effect of geometries and mesh, the pre-test is carried out with various curvature conditions of the bifurcated corner, and then with various mesh conditions. The final process is to calculate flow variables such as the wall shear stress (WSS) and the wall shear stress gradient (WSSG). To validate all the result, the simulation is compared with the existing data of the other papers. Generally speaking, there is a noticeable difference in the maximum and minimum value of WSS. It is not sure that the values in each data are on the exactly same location. However, the overall trend is similar. The next study needs to investigate the same situation by experimental method. Furthermore, if the flow is simulated with more pulsatile conditions, more data of flow field through a bifurcated tube could be achieved.

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THE PERFORMANCE IMPROVEMENT OF VACUUM CLEANER BY ANALYSIS OF THE FLOW AROUND CENTRIFUGAL FAN (진공청소기용 원심팬 주위의 유동해석을 통한 성능개선)

  • Park, J.W.;Ki, M.C.;Park, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.82-87
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    • 2007
  • A cleaner has trouble with too much noise and power consumption. To solve these problems, the investigation for motors, which are the main component of vacuum cleaner, is required. However, it is difficult to analyze the flow by the experimental means because of the high speed of the fan rotation ranging from 30,000 rpm to 50,000 rpm. Moreover it takes much time to perform the numerical simulation for the flow. In this research, it is aimed to analyse the flow through the centrifugal fan which is believed to be a main noise source, by the computational method. The efficiency of the centrifugal fan is affected by friction loss, shock loss and so on. Those losses depend on factors like the velocity of impeller, blade shape and etc. Accordingly, the influence of the shape of impeller on the flow is investigated in this study. The computational analysis was done by changing impeller shapes. The flow around the centrifugal fan is simulated by applying the moving mesh. To verify the validity of the computation results, the air flow rate and the pressure field to the cleaner is compared with the experimental data. All simulations are performed by using commercial code SC/Tetra. The calculated results show good agreement with the experimental ones qualitatively and it is believed to be promising to use computational simulation in the improvement of the vacuum cleaner performance.

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Numerical investigation of flow characteristics through simple support grids in a 1 × 3 rod bundle

  • Karaman, Umut;Kocar, Cemil;Rau, Adam;Kim, Seungjin
    • Nuclear Engineering and Technology
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    • v.51 no.8
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    • pp.1905-1915
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    • 2019
  • This paper investigated the influence of simple support girds on flow, irrespective of having mixing vanes, in a 1 × 3 array rod bundle by using CFD methodology and the most accurate turbulence model which could reflect the actual physics of the flow was determined. In this context, a CFD model was created simulating the experimental studies on a single-phase flow [1] and the results were compared with the experimental data. In the first part of the study, influence of mesh was examined. Tetra, hybrid and poly type meshes were analyzed and convergence study was carried out on each in order to determine the most appropriate type and density. k - ε Standard and RSM LPS turbulence models were used in this section. In the second part of the study, the most appropriate turbulence model that could reflect the physics of the actual flow was investigated. RANS based turbulence models were examined using the mesh that was determined in the first part. Velocity and turbulence intensity results obtained on the upstream and downstream of the spacer grid at -3dh, +3dh and +40dh locations were compared with the experimental data. In the last section of the study, the behavior of flow through the spacer grid was examined and its prominent aspects were highlighted on the most appropriate turbulence model determined in the second part. Results of the study revealed the importance of mesh type. Hybrid mesh having the largest number of structured elements performed remarkably better than the other two on results. While comparisons of numerical and experimental results showed an overall agreement within all turbulence models, RSM LPS presented better results than the others. Lastly, physical appearance of the flow through spacer grids revealed that springs has more influence on flow than dimples and induces transient flow behaviors. As a result, flow through a simple support grid was examined and the most appropriate turbulence model reflecting the actual physics of the flow was determined.

Basic Study on Radio Communication Technology of application for Train Control System (열차시스템에 응용되는 무선통신 기술에 관한 기초연구)

  • Yun, Hak-Sun;Lee, Jong-Woo;Lee, In-Jae;Lee, Kyu-Seoung;Park, Han-Je;Lee, Boo-Hyun
    • Proceedings of the KSR Conference
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    • 2007.11a
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    • pp.1533-1540
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    • 2007
  • The most critical function of the Communication Based Train Control system is wayside and on-board Radio communication. Radio communication must be safely made without errors. The standards for CBTC has not been established yet, and research on Radio communication systems for use in Train control systems adopting CBTC system such as the magnetic levitation train must continue. This paper will discuss the characteristics of Radio communication technology currently used domestically such as GSM-R, IEEE 802.11, TETRA, MESH, and WiMAX/WiBro, and will investigate the potential possibility of applying them to Train control systems.

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A Study on Re-design of Quality Requirements for Disaster Communication Systems (재난통신 체계에 따른 품질요건 재설계에 관한 연구)

  • Yang, Jung-Mo;Kim, Jeong-Ho
    • Journal of Digital Convergence
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    • v.13 no.10
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    • pp.327-335
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    • 2015
  • Wireless mesh networks for public safety and disaster have been developing in a direction from TETRA(TErrestrial Trunked RAdio) to take advantage of the Public Safety-LTE(Long Term Evolution) technology. In Korea, the Disaster Safety Network Building Project has been promoted in order to unify disaster communication systems among disaster response agencies. In this study, the trends of the network construction for national disaster communication and corresponding representative cases of overseas have been analyzed. Through this process, the disaster communication area in line with the purpose of communications. As a result, the disaster communication can be divided into five distinctive areas: the control, the response, the on-site, the victim and the alarm communications. Based on the re-designed communication areas, quality requirements have also been re-organized in this study. Ultimately the construction method for the Disaster Communication systems without exclusion zone will be presented.

PERFORMANCE IMPROVEMENT OF A RANGE HOOD SIROCCO FAN BY CFD FLOW ANALYSIS (렌지후드의 성능개선을 위한 시로코 펜 주위의 유동해석)

  • Han, B.Y.;Park, J.W.;Lee, M.S.;Park, H.K.
    • Journal of computational fluids engineering
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    • v.13 no.4
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    • pp.72-79
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    • 2008
  • This study is to investigate the air flow around a sirocco fan which is used in a range hood. The main object of the study is to improve the flow rate of the fan by analysis of unsteady 3-dimensional incompressible flow. Overall analysis is carried out using CFD method. For this, we used a commercial code, SC/Tetra, and used a sliding mesh method to give the same condition as an actual state. First, verification of the CFD results is done by comparing the experimental data with the numerical data for the suction flow rate. It is confirmed that two results are well consistent. Then for the improvent of flow rate, the effect of shape factors such as diameter ratio of fan, geometry of case, cut-off aperture and guide angle of case exit on the suction flow rate was considered. Especially, for a new design of housing, the principle of Archimedes spiral was used. The overall analysis was applied to a new design of housing, and the result showed an increase of flow rate by 10.7%.